Plasmon tomography

1. A method comprising:

producing plasmon energy by exciting a plasmon resonance at at least one excitation position on a first surface of a first material;

detecting the plasmon energy at at least one measurement position on the first surface after the plasmon energy has propagated from the at least one excitation position to the at least one measurement position;

determining an attenuation of plasmon energy along a plurality of different paths on the first surface and between the at least one excitation position and the at least one measurement position; and

determining relative distances between the first surface and a second surface of a second material at a plurality of points on at least one of the surfaces based on the determined attenuation of plasmon energy along the plurality of paths.

2. The method of claim 1 wherein at least two paths in the plurality of different paths on the first surface are substantially non-overlapping.

3. The method of claim 1 further comprising performing a deconvolution involving the attenuation of plasmon energy along the plurality of different paths on the first surface.

4. The method of claim 1 wherein determining relative distances between the first surface and a second surface at a plurality of points on at least one of the surfaces further includes determining, for a fixed relative position of the first and second surfaces, relative distances between the first surface and the second surface at a plurality of points on at least one of the surfaces.

5. A method comprising:

producing plasmon energy by exciting a plasmon resonance at at least one excitation position on a first surface of a first material, the at least one excitation position having a first x-coordinate and a first y-coordinate;

detecting the plasmon energy at at least one measurement position on the first surface after the plasmon energy has propagated from the at least one excitation position to the at least one measurement position, the at least one measurement position having a second x-coordinate and a second y-coordinate;

determining an attenuation of plasmon energy along a plurality of paths between the at least one excitation position and the at least one measurement position; and

determining relative distances between the first surface and a second surface of a second material at a plurality of points on at least one of the surfaces based on the determined attenuation of plasmon energy along the plurality of paths and respective sets of path coordinates, each defining a respective one of the paths in the plurality of paths.

6. The method of claim 5 wherein determining relative distances between the first surface and the second surface further includes determining, for a fixed relative position of the first and second surfaces, relative distances between the first surface and the second surface.

7. The method of claim 5 wherein the each of the respective sets of path coordinates contains at least one x-coordinate or one y-coordinate distinct from all x-and y-coordinates of at least one other path in the plurality of paths.

8. The method of claim 5 wherein determining relative distances between the first surface and the second surface includes performing a deconvolution based on the determined attenuation of plasmon energy along the plurality of paths and respective sets of path coordinates.

9. The method of claim 5 wherein determining an attenuation of plasmon energy along a plurality of paths includes determining an attenuation of plasmon energy along a plurality of paths for a fixed relative position of the first surface and the second surface.